Bottom Line:
The 4 T1.2 luc3 cell line was found to closely model the sites of metastases seen in human patients including lung, liver, and bone.High osteolytic activity of the 4 T1.2 luc3 cells in vivo in the bone microenvironment was also detected.The engineered 4 T1.2 luc3 and 66c14 luc2 cell lines described in this study are valuable tools for studying the cellular events moderating the metastasis of breast tumor cells to bone.

Background: Tumor cell lines that can be tracked in vivo during tumorigenesis and metastasis provide vital tools for studying the specific cellular mechanisms that mediate these processes as well as investigating therapeutic targets to inhibit them. The goal of this study was to engineer imageable mouse mammary tumor cell lines with discrete propensities to metastasize to bone in vivo. Two novel luciferase expressing cell lines were developed and characterized for use in the study of breast cancer metastasis to bone in a syngeneic mouse model.

Results: The 4 T1.2 luc3 and 66c14 luc2 cell lines were shown to have high levels of bioluminescence intensity in vitro and in vivo after orthotopic injection into mouse mammary fat pads. The 4 T1.2 luc3 cell line was found to closely model the sites of metastases seen in human patients including lung, liver, and bone. Specifically, 4 T1.2 luc3 cells demonstrated a high incidence of metastasis to spine, with an ex-vivo BLI intensity three orders of magnitude above the commercially available 4 T1 luc2 cells. 66c14 luc2 cells also demonstrated metastasis to spine, which was lower than that of 4 T1.2 luc3 cells but higher than 4 T1 luc2 cells, in addition to previously unreported metastases in the liver. High osteolytic activity of the 4 T1.2 luc3 cells in vivo in the bone microenvironment was also detected.

Conclusions: The engineered 4 T1.2 luc3 and 66c14 luc2 cell lines described in this study are valuable tools for studying the cellular events moderating the metastasis of breast tumor cells to bone.

Mentions:
Quantification of the BLI intensities from spines, lung, and liver ex vivo from mice injected with 66c14 luc2, 4 T1.2 luc3, and 4 T1 luc2 cells were performed. Results showed that spines excised from the 4 T1.2 luc3 group had BLI intensities 10-fold higher than the 66c14 luc2 group and three orders of magnitude (103) higher than that of the 4 T1 luc2 injected group (Figure 6A). Lungs from mice injected with either 66c14 luc2 or 4 T1.2 luc3 cells had a mean BLI intensity an order of magnitude higher than the 4 T1 luc2 (Figure 6B). Interestingly, one of the mice injected with 66c14 luc2 cells also showed a high average BLI intensity from multiple metastases in the liver, never previously reported in the parental 66c14 cell line (Figure 6C). Overall, the metastatic burden, which accounts for the average number and size of metastases, detected in vivo and ex vivo was highest for 4 T1.2 luc3 cells. In terms of their ability to be tracked in the primary tumor and secondary metastatic sites in vivo and ex vivo, both 4 T1.2 luc3 and 66c14 luc2 cells showed higher BLI intensities than 4 T1 luc2 cells.

Mentions:
Quantification of the BLI intensities from spines, lung, and liver ex vivo from mice injected with 66c14 luc2, 4 T1.2 luc3, and 4 T1 luc2 cells were performed. Results showed that spines excised from the 4 T1.2 luc3 group had BLI intensities 10-fold higher than the 66c14 luc2 group and three orders of magnitude (103) higher than that of the 4 T1 luc2 injected group (Figure 6A). Lungs from mice injected with either 66c14 luc2 or 4 T1.2 luc3 cells had a mean BLI intensity an order of magnitude higher than the 4 T1 luc2 (Figure 6B). Interestingly, one of the mice injected with 66c14 luc2 cells also showed a high average BLI intensity from multiple metastases in the liver, never previously reported in the parental 66c14 cell line (Figure 6C). Overall, the metastatic burden, which accounts for the average number and size of metastases, detected in vivo and ex vivo was highest for 4 T1.2 luc3 cells. In terms of their ability to be tracked in the primary tumor and secondary metastatic sites in vivo and ex vivo, both 4 T1.2 luc3 and 66c14 luc2 cells showed higher BLI intensities than 4 T1 luc2 cells.

Bottom Line:
The 4 T1.2 luc3 cell line was found to closely model the sites of metastases seen in human patients including lung, liver, and bone.High osteolytic activity of the 4 T1.2 luc3 cells in vivo in the bone microenvironment was also detected.The engineered 4 T1.2 luc3 and 66c14 luc2 cell lines described in this study are valuable tools for studying the cellular events moderating the metastasis of breast tumor cells to bone.

Background: Tumor cell lines that can be tracked in vivo during tumorigenesis and metastasis provide vital tools for studying the specific cellular mechanisms that mediate these processes as well as investigating therapeutic targets to inhibit them. The goal of this study was to engineer imageable mouse mammary tumor cell lines with discrete propensities to metastasize to bone in vivo. Two novel luciferase expressing cell lines were developed and characterized for use in the study of breast cancer metastasis to bone in a syngeneic mouse model.

Results: The 4 T1.2 luc3 and 66c14 luc2 cell lines were shown to have high levels of bioluminescence intensity in vitro and in vivo after orthotopic injection into mouse mammary fat pads. The 4 T1.2 luc3 cell line was found to closely model the sites of metastases seen in human patients including lung, liver, and bone. Specifically, 4 T1.2 luc3 cells demonstrated a high incidence of metastasis to spine, with an ex-vivo BLI intensity three orders of magnitude above the commercially available 4 T1 luc2 cells. 66c14 luc2 cells also demonstrated metastasis to spine, which was lower than that of 4 T1.2 luc3 cells but higher than 4 T1 luc2 cells, in addition to previously unreported metastases in the liver. High osteolytic activity of the 4 T1.2 luc3 cells in vivo in the bone microenvironment was also detected.

Conclusions: The engineered 4 T1.2 luc3 and 66c14 luc2 cell lines described in this study are valuable tools for studying the cellular events moderating the metastasis of breast tumor cells to bone.